Archived Research Updates

Study links normal function of protein, not its build up inside cells, to death of neurons

A new study led by St. Jude Children's Research Hospital scientists signals hope for treatment of a neurodegenerative disease and a new model for understanding the mechanism at work in other more common neurodegenerative disorders

A study led by St. Jude Children's Research Hospital investigators links the muscle weakness and other symptoms of a rare neurodegenerative disease to a misstep in functioning of a normal protein, rather than its build-up inside cells. The finding offers insight into the mechanism driving common nervous system disorders like Parkinson's and Alzheimer's diseases.

The work advances understanding of how the inherited mistake at the heart of spinobulbar muscular atrophy (SBMA) leads to the death of neurons in the brain and spinal cord. Investigators showed that the underlying mutation caused an amplification of the protein's normal function. The work appears in the September 23 online edition of the scientific journal Neuron.

"The idea that toxicity is mediated by the native, or normal, function of the protein itself is a departure from conventional wisdom. This research adds to growing evidence the principle applies very broadly in other neurodegenerative disorders, including Alzheimer's and Parkinson's diseases," said J. Paul Taylor, M.D., Ph.D., an associate member in the St. Jude Department of Developmental Neurobiology and the paper's senior author.

The current neurodegenerative disease model links the disorders to a toxic build-up of improperly folded proteins inside cells. Taylor said: "Our findings suggest the focus on protein aggregation inside cells may be misplaced." Developing therapies that target the normal protein function will likely be easier and more effective, he added.

Medications are already available to block the androgen receptor (AR) protein, which is mutated in SBMA. Work is now underway in Taylor's laboratory to identify drugs that more selectively block AR functioning.

SBMA belongs to a family of eight disorders, including Huntington's disease, which stem from an overabundance of the same small, repeated sequence of DNA known as a trinucleotide. Such repetitions are common throughout the genome, but problems arise when they occur too frequently. That is what happens in the estimated 1 in 50,000 males with SBMA.

In the case of SBMA, the repeated sequence occurs in the gene for the androgen receptor. The repeated nucleotide sequence CAG is protein-production shorthand for an amino acid called glutamine. The resulting androgen receptor (AR) protein includes surplus glutamine.

After earlier work by other investigators showed that blocking testosterone prevented male mice with the SBMA mutation from developing the disease, Taylor and his colleagues set out to track what happened inside cells after the hormone bound to the mutated AR protein.

Working in a Drosophila fruit fly model of the disease, the scientists identified a small region of the AR protein, known as the AF-2 domain, which played a pivotal role.

Using a variety of techniques, researchers demonstrated they could rescue the cells by preventing certain members of a family of proteins called coregulators from binding to the AF-2 domain. Coregulators partner with AR and other transcription factors to regulate gene expression.

"In this study, we showed the ability of the mutant protein to interact with the normal binding partners is an essential step in the cascade of degeneration. By blocking it, we block degeneration," Taylor said. He added that the AF-2 domain is far from the mutated region of the AR protein. "That would be unexpected if the mechanism of toxicity were related to the protein aggregating," he explained.

Meanwhile, investigators are still studying why the protein's change in function is so deadly to cells. Taylor noted that research into inherited diseases like SBMA has historically provided important clues into the mechanisms at work in other more common neurodegenerative disorders, including Alzheimer's.

The findings also hold hope that treating or preventing SBMA by selectively disrupting AF-2 binding will soon be possible, Taylor said. "Selectively blocking the hormone will be key if we hope to prevent the side effects associated with androgen ablation in males," he said. The side effects include bone thinning, infertility or blocked sexual maturation.

The study also suggests the need to begin treatment earlier. If the damage to motor neurons begins with the hormone surge of puberty rather than the accumulation of mis-folded proteins, therapies must begin in childhood, Taylor said.

Natalia Nedelsky, of St. Jude and the University of Pennsylvania, is the study's first author. The co-authors are Maria Pennuto, Italian Institute of Technology, Genoa, Italy; Isabella Palazzolo, National Institute of Neurological Disorders and Stroke; Zhiping Nie, University of Pennsylvania; and Rebecca Smith, Jennifer Moore and Geoffrey Neale, all of St. Jude.

The study was funded in part by the Muscular Dystrophy Association, the Kennedy's Disease Association, the National Institutes of Health and ALSAC.

St. Jude Children's Research Hospital

St. Jude Children's Research Hospital is internationally recognized for its pioneering research and treatment of children with cancer and other catastrophic diseases. Ranked the No. 1 pediatric cancer hospital by Parents magazine and the No. 1 children's cancer hospital by U.S. News & World Report, St. Jude is the first and only National Cancer Institute-designated Comprehensive Cancer Center devoted solely to children. St. Jude has treated children from all 50 states and from around the world, serving as a trusted resource for physicians and researchers. St. Jude has developed research protocols that helped push overall survival rates for childhood cancer from less than 20 percent when the hospital opened to almost 80 percent today. St. Jude is the national coordinating center for the Pediatric Brain Tumor Consortium and the Childhood Cancer Survivor Study. In addition to pediatric cancer research, St. Jude is also a leader in sickle cell disease research and is a globally prominent research center for influenza.

Founded in 1962 by the late entertainer Danny Thomas, St. Jude freely shares its discoveries with scientific and medical communities around the world, publishing more research articles than any other pediatric cancer research center in the United States. St. Jude treats more than 5,700 patients each year and is the only pediatric cancer research center where families never pay for treatment not covered by insurance. St. Jude is financially supported by thousands of individual donors, organizations and corporations without which the hospital's work would not be possible. In 2010, St. Jude was ranked the most trusted charity in the nation in a public survey conducted by Harris Interactive, a highly respected international polling and research firm. For more information, go to www.stjude.org.

Contact: Summer Freeman

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IGF1 might work better and more specifically in Kennedy's disease than in ALS says ... Kennedy's disease also called spinal and bulbar muscular atrophySBMA

October 19, 2009

Rescuing SBMA-Affected Muscles - Maria Pennuto

January 7, 2009

Researchers Explore Self-Defense in Nerve Cells for SBMA Click Here for full article

January 17, 2008

Two grants just funded by the KDA both attempt to investigate mechanisms to prevent the accumulation of the toxic fragment in cells containing the mutant AR.

Briefly, KD is caused by a genetic mutation to the gene that codes for the Androgen Receptor (AR) protein. This protein mediates all the actions of the androgen hormones testosterone and dihydrotestosterone, DHT. In the cells of normal males, the AR is found in the cytoplasm of the cell. Upon the addition of an androgen hormone (either testosterone or DHT), the hormone binds to the AR and the hormone/AR complex travels to the nucleus of the cell where it initiates the masculine changes that are associated with the presence of androgens (beard growth, for example). If there is no androgen present, then the AR never enters the nucleus and there are no changes – this is essentially what occurs in females. Since women do not possess androgens, the AR does nothing in cells and there are no masculine effects. The AR in the nucleus is ultimately destroyed by a cell structure known as the proteasome. In individuals with KD, the cell is unable to completely destroy the AR that enters the nucleus - but it can destroy the AR that does not enter the nucleus and this inadequate digestion apparently results in the production of a fragment of the mutant AR that is toxic to the cells – thus the cells die and this leads to the formation of the symptoms of KD. This appears to explain why women carriers do not show major symptoms. Since the levels of androgens in women are low, the mutant AR does not enter the nucleus and the cell does not create the toxic fragment.

A $25,000 grant was awarded to Maria Pennuto, Ph.D. from the National Institute of Health. Dr. Pennuto has spent the past few years investigating the molecular switches on the AR that are involved in the movement of the AR into the nucleus upon addition of hormone. She has discovered that certain chemical changes to the AR seem to reduce the ability of the AR to bind to hormone and thus not enter the nucleus (and cause KD!!). She has discovered that the exposure of cells to a substance known as IGF-1 can induce these chemical changes to occur to the mutant AR and thus prevent the movement of the AR to the nucleus. Thus, the addition of IGF-1 to a cell with mutant AR appears to prevent the formation of the toxic fragment and thus the cell stays alive. Dr. Pennuto will continue this work by determining if any other chemical changes to the AR may alter its movement to the nucleus and she will also determine if IGF-1 prevents the formation of KD symptoms in a KD mice model (up to this time, the effect of IGF-1 has only been shown to work in cell cultures. This work could lead to new therapies for KD.

Another $25,000 grant was awarded to Udai Bhan Pandey, Ph.D. from the University of Pennsylvania. The proposal by Dr. Pandey and Dr. Paul Taylor continues the work that they did (in part thanks to a previous KDA grant!). They previously reported that KD symptoms in a fly model of KD could be reduced by activating another mechanism for destroying the KD in the nucleus, by passing the need for the proteasome. This alternate pathway, known as autophagy, apparently is capable of destroying the toxic fragment. They did this by making the fly over produce another protein known as HDAC6. By doing this, they were able to demonstrate that the overproduction of HDAC6 did not show cell death despite the presence of the mutant KD. They will now try to continue this work as they attempt to find other proteins that may affect this activity of HDAC6 to stimulate autophagy and thus help prevent the cell death associated with KD.

Each received grants of $25,000. Their work has been reported on regularly and is aiding in the attempt to find a treatment or cure for Kennedy's Disease. The KDA also thanks all the researchers who have dedicated themselves to this cause as well as our Associates, businesses, and friends who continue to support the funding of these grants.

March 27, 2007

Two interesting papers, well, interesting to those with KD, were published during the past several weeks. Read more here

The first paper is Soluble Androgen Receptor Oligomers Underlie Pathology in a Mouse Model of Spinobulbar Muscular Atrophy.by Li, Chevalier-Larsen, Merry and Diamond.

A second paper recently published on KD, well actually, it is about Huntington’s Disease, is “Ubiquitin-Interacting Motifs Inhibit Aggregation of Poly Q-Expanded Huntingtin” by Miller, Scappini and O’Bryan

March 20, 2007

KDA Funded Research Update

Chawnshang Chang, Ph.D. and a team of researchers at the University of Rochester Medical Center have published the attached news release concerning their research that could potentially lead to a treatment for Kennedy's Disease. The article was published in the March 6 issue of the journal Nature Medicine. Read more here

Thanks to the generous support of our associates, Dr. Chang received a $25,000 research grant from the Kennedy's Disease Association last fall.

March 2, 2007 - 2 Articles

SBMA Mice Answer some questions, Raise others.

Please follow the link to the article. Note: This research article speaks of Andrew Lieberman's lab research. Andrew Lieberman is on the Kennedy's Disease Association's Scientific Review Board.. Click here to go to the article.

Announcing the results of a University of Michigan research study that is related to Kennedy's Disease. The research project was partially funded by the KDA through the generous donations of our associates, their family, and friends.

For the first time, researchers have enticed transplants of embryonic stem cell-derived motor neurons in the spinal cord to connect with muscles and partially restore function in paralyzed animals. The study suggests that similar techniques may be useful for treating such disorders as spinal cord injury, transverse myelitis, amyotrophic lateral sclerosis (ALS), and spinal muscular atrophy.

The study was funded in part by the NIH’s National Institute of Neurological Disorders and Stroke (NINDS). The full story appears online at www.nih.gov/news/pr/jun2006/ninds-20.htm or by accessing the main news section of the NINDS and NIH websites.

Notice: The Annals of Neurology has lifted the news embargo for this article.

July 31, 2005 In Year 2002, the KDA sent a questionnaire to all current KDA Associates. There were hundreds of questions to try to get a snapshot of KD symptoms, lifestyles, etc. 34 responded and the results have been painstakingly tallied. Click Here to see the compiled reports.

June 2004 KDA funded research grant update - The KDA funded a grant to J. Paul Taylor, MD PhD at University of Pennsylvania for $25,000 in November 2003 for a Drosophila melanogaster (fruitfly) model system to investigate the molecular pathogenesis of Spinal and Bulbar Muscular Atrophy. Dr. Taylor has provided us with an update as to how their research is coming along. Please Click Here to read the update.

KDA awards Andrew Lieberman, PhD at University of Michigan a research grant in the amount of $25,000 in January 2004

KDA awards J. Paul Taylor, MD, PhD at University of Pennsylvania a research grant in the amount of $25,000 in November 2003

April 2003 - Possible drug treatment for Kennedy's may be on the horizon Scientists Search for Drugs to help Kennedy's Disease At the 55th Annual meeting of the American Academy of Neurology, scientists reported that they've scored multiple "hits" in a screen for drugs that might be useful against Kennedy's disease.

Studies indicate that ligand, i.e. testosterone, is responsible for setting in action the toxic effects of the expanded repeat androgen receptor in KD mouse models. This is an important finding that indicates that testosterone may NOT be a good therapy for KD. A reduction of testosterone in this mouse model of Dr. Sobue's reduced the toxic effects of the mutant androgen receptor.

However, the use of antagonists (drugs that counter the effect of testosterone) to the androgen receptor are not warranted either, as the accompanying paper on a fly model of SBMA shows that the use of antagonists that promote the transfer of the receptor into the nucleus of the cell (which testosterone does), also promotes disease symptoms. Please see the links to the files below. They are fairly large files and may take a few minutes to download depending on your connection speed so please be patient.

The below files are Adobe Acrobat files. You will need to download Adobe Acrobat viewer if have not already done so. Go to www.adobe.com to get the viewer - click on the "Download Acrobat Reader" under the "Support" section.

We performed microarray analysis of lower hindlimb muscles taken from these three models relative to wild type controls using high density oligonucleotide arrays. All microarray comparisons were made with at least 3 animals in each condition, and only those genes having at least 2-fold difference and whose coefficient of variance was less than 100% were considered to be differentially expressed. When considered globally, there was a similar overlap in gene changes between the 3 models: 19% between HSA-AR and AR97Q, 21% between AR97Q and AR113Q, and 17% between HSA-AR and AR113Q, with 8% shared by all models. Several patterns of gene expression relevant to the disease process were observed. Notably, patterns of gene expression typical of loss of AR function were observed in all three models, as were alterations in genes involved in cell adhesion, energy balance, muscle atrophy and myogenesis. We additionally measured changes similar to those observed in skeletal muscle of a mouse model of Huntington’s Disease, and to those common to muscle atrophy from diverse causes.

Conclusions/Significance

By comparing patterns of gene expression in three independent models of KD/SBMA, we have been able to identify candidate genes that might mediate the core myogenic features of KD/SBMA.

Sept 23, 2010

Study links normal function of protein, not its build up inside cells, to death of neurons

A new study led by St. Jude Children's Research Hospital scientists signals hope for treatment of a neurodegenerative disease and a new model for understanding the mechanism at work in other more common neurodegenerative disorders

A study led by St. Jude Children's Research Hospital investigators links the muscle weakness and other symptoms of a rare neurodegenerative disease to a misstep in functioning of a normal protein, rather than its build-up inside cells. The finding offers insight into the mechanism driving common nervous system disorders like Parkinson's and Alzheimer's diseases.

The work advances understanding of how the inherited mistake at the heart of spinobulbar muscular atrophy (SBMA) leads to the death of neurons in the brain and spinal cord. Investigators showed that the underlying mutation caused an amplification of the protein's normal function. The work appears in the September 23 online edition of the scientific journal Neuron.

"The idea that toxicity is mediated by the native, or normal, function of the protein itself is a departure from conventional wisdom. This research adds to growing evidence the principle applies very broadly in other neurodegenerative disorders, including Alzheimer's and Parkinson's diseases," said J. Paul Taylor, M.D., Ph.D., an associate member in the St. Jude Department of Developmental Neurobiology and the paper's senior author.

The current neurodegenerative disease model links the disorders to a toxic build-up of improperly folded proteins inside cells. Taylor said: "Our findings suggest the focus on protein aggregation inside cells may be misplaced." Developing therapies that target the normal protein function will likely be easier and more effective, he added.

Medications are already available to block the androgen receptor (AR) protein, which is mutated in SBMA. Work is now underway in Taylor's laboratory to identify drugs that more selectively block AR functioning.

SBMA belongs to a family of eight disorders, including Huntington's disease, which stem from an overabundance of the same small, repeated sequence of DNA known as a trinucleotide. Such repetitions are common throughout the genome, but problems arise when they occur too frequently. That is what happens in the estimated 1 in 50,000 males with SBMA.

In the case of SBMA, the repeated sequence occurs in the gene for the androgen receptor. The repeated nucleotide sequence CAG is protein-production shorthand for an amino acid called glutamine. The resulting androgen receptor (AR) protein includes surplus glutamine.

After earlier work by other investigators showed that blocking testosterone prevented male mice with the SBMA mutation from developing the disease, Taylor and his colleagues set out to track what happened inside cells after the hormone bound to the mutated AR protein.

Working in a Drosophila fruit fly model of the disease, the scientists identified a small region of the AR protein, known as the AF-2 domain, which played a pivotal role.

Using a variety of techniques, researchers demonstrated they could rescue the cells by preventing certain members of a family of proteins called coregulators from binding to the AF-2 domain. Coregulators partner with AR and other transcription factors to regulate gene expression.

"In this study, we showed the ability of the mutant protein to interact with the normal binding partners is an essential step in the cascade of degeneration. By blocking it, we block degeneration," Taylor said. He added that the AF-2 domain is far from the mutated region of the AR protein. "That would be unexpected if the mechanism of toxicity were related to the protein aggregating," he explained.

Meanwhile, investigators are still studying why the protein's change in function is so deadly to cells. Taylor noted that research into inherited diseases like SBMA has historically provided important clues into the mechanisms at work in other more common neurodegenerative disorders, including Alzheimer's.

The findings also hold hope that treating or preventing SBMA by selectively disrupting AF-2 binding will soon be possible, Taylor said. "Selectively blocking the hormone will be key if we hope to prevent the side effects associated with androgen ablation in males," he said. The side effects include bone thinning, infertility or blocked sexual maturation.

The study also suggests the need to begin treatment earlier. If the damage to motor neurons begins with the hormone surge of puberty rather than the accumulation of mis-folded proteins, therapies must begin in childhood, Taylor said.

Natalia Nedelsky, of St. Jude and the University of Pennsylvania, is the study's first author. The co-authors are Maria Pennuto, Italian Institute of Technology, Genoa, Italy; Isabella Palazzolo, National Institute of Neurological Disorders and Stroke; Zhiping Nie, University of Pennsylvania; and Rebecca Smith, Jennifer Moore and Geoffrey Neale, all of St. Jude.

The study was funded in part by the Muscular Dystrophy Association, the Kennedy's Disease Association, the National Institutes of Health and ALSAC.

Abstract

BACKGROUND: Spinal and bulbar muscular atrophy is a hereditary motor neuron disease caused by the expansion of a polyglutamine tract in the androgen receptor. At present there are no treatments for spinal and bulbar muscular atrophy, although leuprorelin suppressed the accumulation of pathogenic androgen receptors in a phase 2 trial. We aimed to assess the efficacy and safety of leuprorelin for spinal and bulbar muscular atrophy. METHODS: The Japan SBMA Interventional Trial for TAP-144-SR (JASMITT) was a 48-week, randomised, double-blind, placebo-controlled trial done at 14 hospitals between August, 2006, and March, 2008. Patients with spinal and bulbar muscular atrophy were randomly assigned (1:1) by minimisation to subcutaneous 11.25 mg leuprorelin or identical placebo every 12 weeks. Patients and investigators were masked to treatment allocation. The primary endpoint was pharyngeal barium residue, which indicates incomplete bolus clearance, measured at week 48 by videofluorography. All patients who were randomly assigned and who were assessed with videofluorography at least once were included in the analyses. This study is registered with the JMACCT clinical trials registry, number JMA-IIA00009, and the UMIN clinical trials registry, number UMIN000000465. FINDINGS: 204 patients were randomly assigned and 199 started treatment: 100 with leuprorelin and 99 with placebo. At week 48, the pharyngeal barium residue after initial swallowing had changed by -5.1% (SD 21.0) in the leuprorelin group and by 0.2% (18.2) in the placebo group (difference between groups -5.3%; 95% CI -10.8 to 0.3; p=0.063). The mean difference in pharyngeal barium residue after piecemeal deglutition at week 48 was -3.2% (-6.4 to 0.0; p=0.049), but there was no significant difference between the groups after covariate adjustment for the baseline data (-4.1 to 1.6; p=0.392). In a predefined subgroup analysis, leuprorelin treatment was associated with a greater reduction in barium residue after initial swallowing than was placebo in patients with a disease duration less than 10 years (difference between groups -9.8, -17.1 to -2.5; p=0.009). There were no significant differences in the number of drug-related adverse events between groups (57 of 100 in the leuprorelin group and 54 of 99 in the placebo group; p=0.727).

INTERPRETATION: 48 weeks of treatment with leuprorelin did not show significant effects on swallowing function in patients with spinal and bulbar muscular atrophy, although it was well tolerated. Disease duration might influence the efficacy of leuprorelin and thus further clinical trials with sensitive outcome measures should be done in subpopulations of patients. FUNDI